Engine revving

While driving with cruise control set at 80 mph in my 2002 Toyota Camry,the engine suddenly revved up to 4200 rpm while going up a hill on the freeway. I was wondering if this sudden high rpm could do damage to the engine? The car has 163,000 miles on it.

What is the “red line” point on your tachometer?
If, as I suspect, the engine is redlined at ~6,500 RPMs, then no damage would take place on a warmed-up engine turning 4,200 RPMs. Additionally, the ECM would most likely cut off the fuel flow if the engine reached its red line RPM limit.

However, you need to clarify exactly what happened when the engine began revving very high.
Did the car gain speed, or did it maintain its speed, or did it slow down?

I have less concern for the engine in this case than for the transmission, which may be slipping.
What can you tell us about the maintenance record for the transmission?

Going up a hill ?
Did the transmission simply downshift ?


I also suspect that the transmission merely downshifted, but 4,200 RPMs seems a bit high for a downshift of just one gear.

Your transmission downshifted. With the cruise set at 80, 4200rpm doesn’t surprise me. The redline is probably about 6-6,500. If its under the redline there’s nothing to worry about. The engine has a rev limiter anyway. But you’re better off leaving the cruise off for significant grades. Cruise control systems are a little bit “dumb.” It’s also the case that, while the downshift and 4200 rpm isn’t “bad” - its more wear on both the engine and transmission then if it hadn’t downshifted and you’d just lost some speed instead. That’s what your foot allows, but the cruise is a little “dumb” about. If you set it at 80 it will want to do 80 - into a brick wall if that’s what happens to be there.

I agree. It upsets my wife when we (me, she never uses it) uses the cruise control and it suddenly downshifts to maintain speed on a hill. She thinks we are all of a sudden going way too fast and the world is coming to an end. After a little screaming and yelling at me to slow down, we have the umpteenth discussion about the vehicle not self distructing, it’s protected by a computer with an engine red line of over 6 k and the motor is still a thousand or so below it. Everything is fine until the next hill, the next scream and we start all over again…" women, can’t live with’m, pass the beer nuts". I love her dearly, more then life itself…except when I’m driving and that downshift occurs. One of the few times I wish the car would lug and just slow down.

Now my question. Where the heck are you driving with a cruise set at 80mph ?

The Interstate speed limits where I live are 65mph, trucks 55mph. I have driven in other states where they are 75mph including trucks. If this is the case 80mph is not out of line although at that speed I would at least ensure my tires were up to the task.

Thanks for the feedback. I appreciate it.

Climbing a long incline implies some elevation above sea level, so the engine is breathing thin air, less power.
Four cylinder engine? 4200rpm is reasonable to deliver the power to climb a hill at 80mph.